In 3GPP (3rd Generation Partnership Project), W-CDMA (Wideband Code Division Multiple Access) is standardized as a third generation cellular mobile communication system. Then, W-CDMA's service is sequentially started. In addition, HSDPA (High Speed Downlink Packet Access) which has further increased communication speed, is also standardized. Then, HSDPA's service will be started.
In the 3GPP, the evolution of third generation wireless access (EUTRA: Evolved Universal Terrestrial Ratio Access) is discussed.
In a downlink of the EUTRA, an OFDM (Orthogonal Frequency Division Multiplexing) system is proposed. In addition, as an uplink of the EUTRA, a single carrier communication system of a DFT (Discrete Fourier Transform)-spread OFDM system is proposed.
As shown in FIG. 20, a base station BS performs wireless communications with a plurality of mobile station devices MS1, MS2 and MS3. The downlink of the EUTRA includes a downlink pilot channel DPich, a downlink synchronization channel DSCH, a physical downlink control channel PDCCH, a physical downlink shared channel PDSCH and a common control physical channel CCPCH.
The uplink of the EUTRA includes an uplink pilot channel UPiCH, a random access channel RACH, a physical uplink shared channel PUSCH and a physical uplink control channel PUCCH (Non-Patent Documents 1 and 2).
As the random access channel RACH, there are a non-synchronization random access channel and a synchronization random access channel. A minimum unit of the non-synchronization random access channel uses 1.25 MHz band, prepares a plurality of channels for access, and copes with a plurality of accesses. FIG. 21 is one example.
In FIG. 21, the horizontal axis is time, and the longitudinal axis is frequency. FIG. 21 represents one communication frame of the uplink. The frame is divided into a plurality of resource blocks. One resource block comprises 1 ms of time and 1.25 band of frequency. The random access channel is assigned to the resource blocks shown in the left-diagonal-line-hatched regions. The uplink common channel is assigned to the resource blocks which shown in the blank regions. The uplink control channel is assigned to the resource blocks which shown in the right-diagonal-line-hatched regions.
A purpose of the non-synchronization random access channel is to synchronize the mobile station device and the base station device, and it is possible to shorten the connection time by transmitting a few bits which are a scheduling request for assigning wireless resources. In addition, a purpose of the synchronization random access is to request scheduling (Non-Patent Document 2).
As a non-synchronization access, there are two access methods (a contention based random access and a non-contention base random access). The contention based random access is random access which may cause contention between mobile station devices, is usually performed. The non-contention based random access is random access which does not cause contention, and is performed in a special case for rapidly synchronizing the mobile station device and the base station device by a instruction of the base station device.
In non-synchronization random access, a preamble is only transmitted for synchronizing an uplink. The preamble includes a signature which is a signal pattern representing information, and is able to represent few bit information by using dozens of signatures. If six bit information is transmitted, 64 kinds of signatures are used.
In the six bit information, five bits are assigned a random ID (Identity), and rest one bit is assigned information (for example, pass loss, CQI (Channel Quality Indicator of downlink)) (Non-Patent Document 3).
FIG. 22 is a processes of the contention random access of the non-synchronization random access.
First, the mobile station device selects a signature among a random ID, a pass loss/CQI of downlink, and transmits a random access preamble using the non-synchronization random access channel of downlink (process PRC 1001). When the base station device receives the preamble from the mobile station device, the base station device calculates a synchronization timing shift between the mobile station device and the base station device based on the preamble. Then the base station device performs scheduling for transmitting a L2/L3 (Layer 2/Layer 3). Then the base station device assigns a temporary C-RNTI to the mobile station device which needs C-RNTI (Cell-Ratio Network Temporary Identity) based on a random access reason in the random access preamble. Then the base station device transmits synchronization timing shift information, scheduling information, and a random access response which includes the C-RNTI and a signature ID number (process PRC 1002).
The mobile station device abstracts response of the base station which includes transmitted a signature ID. Then, the mobile station device transmits the L2/L3 message using wireless recourse scheduled based on the scheduling information (process PRC 1003). The base station device receives the L2/L3 message form the mobile station device, and transmits, to the mobile station device, a contention resolution for determining whether or not contention has occurred between mobile station devices (process PRC 1004). This technology is disclosed in the Non-Patent Document 3.
FIG. 23 shows processes of non-contention random access of the non-synchronization random access.
First, the base station device selects a signature and transmits it to the mobile station device (process PRC 2001). The mobile station device transmits a random access preamble on a non-synchronization random access channel using a sent signature (process PRC 2002). The base station device calculates the synchronization timing shift between the mobile station device and the base station device when the base station device receives the preamble from the mobile station device, and transmits a random access response which includes a C-RNTI or an RA-RNTI (Random Access-Radio Network Temporary Identity) (process PRC 2003). The mobile station device corrects the synchronization timing shift based on the received message 3 (Non-Patent Document 3). The C-RNTI or RA-RNTI is one kind of identification.
As the uplink pilot channel UPiCH, there are two kind of reference signals. In other words, there is a reference signal which is used for measuring (sounding Reference Signal) and a reference signal for demodulating (demodulated Reference signal). The reference signal which is used for measuring is used as a reference signal which estimates a channel for scheduling of an uplink. The reference signal which is used for measuring is used to perform data scheduling. Therefore, the reference signal which is used for measuring is assigned a wide transmission band which is wider than a band of data transmission, and is regularly and separately transmitted from data transmission. The reference signal which is used for measuring is described later.
The reference signal for demodulating is used as a reference signal which estimates a channel for scheduled data demodulation. The reference signal for demodulating is used to perform data demodulation. Therefore the reference signal for demodulating is only transmitted in a transmission band which is same as a band of data.
The uplink pilot channel UPiCH may be used to perform synchronization maintenance of an uplink between a mobile station device which transmits data in the uplink and a base station device. The base station device calculates a synchronization timing shift between the mobile station device and the base station device based on the uplink pilot channel UPiCH like a preamble of the random access channel RACH, and sends the synchronization timing shift information to the mobile station device (Non-Patent Document 4).
FIG. 24 is a diagram showing each state transition of an uplink synchronization establishment, a synchronization maintenance and a synchronization deviation. FIG. 25 is a diagram showing the synchronization maintenance in detail.
First, in FIG. 24, the mobile station device performs a non-synchronization random access of contention random access, and synchronizes the base station device and the mobile station device of the uplink (process PRC 3001). While uplink data is transmitted, only the base station device manages the uplink synchronization, and the base station device measures the uplink pilot channel UPiCH (especially, a reference signal which is used for measuring) and calculates a synchronization timing shift, and the uplink synchronization maintained by the base station device sends the synchronization timing shift information to the mobile station device (process PRC 3002). If data transmission is finished, a synchronization management of the uplink is performed by the base station device and the mobile station device, and the synchronization is maintained for a predetermined period (process PRC 3003). After the predetermined period is over (process PRC 3004), the synchronization is deviated, and the mobile station device performs non-synchronization random access again to synchronize (process PRC 3004).
The uplink control channel PUCCH is used to transmit ACK (Acknowledgment)/NACK (Negative Acknowledgment) for the downlink data, or is used to transmit a CQI of the downlink for a downlink data scheduling.
The retransmission number is decreased by using HARQ (Hybrid Automatic Repeat reQuest) to data packet of the uplink common channel PUSCH, and by increasing error correction ability of retransmission. In common ARQ (Automatic Repeat reQuest), if an error occurs in receiving packet data, the error-containing packet is destroyed, and the retransmission of the same packet is requested. In contrast, high speed hybrid automatic repeat request is a technique for performing the error recovery by storing the error-containing packet and synthesizing the retransmitted packet data. In a high speed hybrid automatic repeat request, there is a chase synthesis and an IR (Incremental Redundancy) synthesis.
Non-Patent Document 1: 3GPP TS (Technical Specification) 36.211, V1.10 (2007-05), Technical Specification Group Radio Access Network, Physical Channel and Modulation (Release 8)
Non-Patent Document 2: 3GPP TS (Technical Specification) 36.212, V1.20 (2007-05), Technical Specification Group Radio Access Network, Multiplexing and channel coding (Release 8)
Non-Patent Document 3: R2-072338 “Update on Mobility, Security, Random Access Procedure, etc”, 3GPP TSG RAN WG2 Meeting #58 Kobe, Japan, 7-11 May, 2007
Non-Patent Document 4: 3GPP TR (Technical Report) 25.814, V7.0.0 (2006-06), Physical layer aspects for evolved Universal Terrestrial Radio Access (UTRA)